The Glycemic Load is the most practical way to apply the Glycemic Index to dieting, and is easily calculated by multiplying a food’s Glycemic Index (as a percentage) by the number of net carbohydrates in a given serving. Glycemic Load gives a relative indication of how much that serving of food is likely to increase your blood-sugar levels.

GL = GI/100 x Net Carbs

(Net Carbs are equal to the Total Carbohydrates minus Dietary Fiber)

As a rule of thumb, most nutritional experts consider Glycemic Loads below 10 to be “low,” and Glycemic Loads above 20 to be “high.” Because Glycemic Load is related to the food’s effect on blood sugar, low Glycemic Load meals are often recommended for diabetic control and weight loss.

Note:

For a more extensive discussion of Glycemic Index and Glycemic Load, please see ND’s Glycemic Index page.

Limitations to Glycemic Load’s Use

To calculate Glycemic Load, you must first determine the food’s Glycemic Index (GI), which can only be done via human testing. GI testing is relatively expensive and very time-consuming. Human test subjects are required, and only a limited number of laboratories currently perform these tests. Consequently, GI data is only available for a very small percentage of the foods that we consume.

The most prolific GI testing laboratory is based in Australia, so a large portion of the currently tested foods are of Australian origin. This further limits the usability of the data, because some of the tested foods do not have equivalent forms in the U.S. or other parts of the world.

To make matters worse, food manufacturers are creating new food products at a much faster rate than GI testing can be performed. Each year, tens of thousands of new packaged-food items are added to grocery shelves, but only a few hundred foods are tested for GI. Because of this, it’s doubtful that we’ll ever reach a point in time where GI is known for all foods.

In addition to these limitations, there is no recognized method for accurately determining GI for recipes, other than to submit the prepared recipe for the previously described human tests. The consequence of this is that a chef or home cook has no practical way to determine the Glycemic Index or Glycemic Load for any of his own creations.

Clearly, what is needed is a way to estimate Glycemic Load when Glycemic Index is unknown.

Extending Glycemic Load with Estimated ValuesBy doing a multivariate analysis on the existing glycemic data, Nutrition Data was able to create a mathematical formula that estimates Glycemic Load by comparing the food’s levels of commonly known nutrients. This formula was not intended to completely replace traditional Glycemic Load calculations, but it does produce a reasonable estimation when a food’s Glycemic Index is unknown.

Below is a graph that displays a comparison between actual and estimated Glycemic Loads for over 200 common carbohydrate-containing foods.